l82 



KNOWLEDGE & SCIENTIFIC NEWS. 



fjULY, 1905. 



to the steel work and anchoring' them back in the solid 

 rock behind, and as the electric cranes standing- on the 

 completed portion built the bridge forwards, extra 

 cables were affixed until, on April ist last, the two 

 halves met. 



The process by which the Zambezi has cut its erratic 

 course has been traced by Mr. A. J. C. Molyneux in the 

 Geographical Journal * The basalt rock, when cooling, 

 developed cracks and fissures, due to contraction, and 

 i'.ssumed the columnar form. The cutting back of the 

 falls is concluded to be due to the water falling down 

 upon and into these cracks; with the constant vibration 

 the columns are rent asunder and fall in huge flakes into 

 the chasm. Little evidence is seen of the rock being 

 worn away by attrition, the blocks newly fallen into the 

 chasm still retaining their sharp angles. Tliesc block.s 

 gradually disappear into the Grand Canon impelled by 

 the rush of the current, and are constantly grinding 

 down and deepening the bed, to emerge as rounded 

 pebbles at the eastern end. 



The zigzags are held to be due partly to the position 

 of the islands that studded the river (as now), and to the 

 existence of master joints and fissures in the basalt. 

 Where an island occurs there the erosive action of the 

 water has no effect, hence the extraordinary isolated 

 bluffs and knife edges of rock connecting them. There 

 are no signs that the earth was cracked in this form by 

 some seismic convulsion, or that a material softer than 

 the surrounding basalt has been eaten away by the 

 action of the water. 



One of the chief glories of the falls is the wealth of 

 colour, not only in the rich foliage of the tropical vege- 

 tation, or the dazzling white masses of tumbling foam, 

 but in the prismatic Ix>ws sparkling in the mist. When 

 walking between the forest and the chasm, a small bow 

 may be seen almost within touch of the hand, and 

 faithfully following; then there is the more ordinary 

 type spanning the gorge or irradiating the gloomy 

 depths below, and rendered especially beautiful by the 

 soft rays of the moon. 



Many members of the British Association who are 

 visiting- South Africa intend to travel as far 

 north as the Zambezi. TTic climate at that season 

 of the year will be found dry and warm, while mos- 

 quitoes and fever are happily absent. The volume of 

 water, too, has been diminishing since May, conse- 

 quently the curtain of spray will be in great measure 

 drawn aside, disclosing the beauties of the falling 

 water and the depths of the chasm. 



• Vol. XXV., No. I, 1905. 



South Africa.n Association for the 

 Advancement of Science. 



From a suggestion to arrange for an Annual Congress of 

 Engineers in South Africa arose the larger idea of a federated 

 body in science on the model of the home British Association. 

 The first practical step was taken in March, 1901, at a meet- 

 ing held in Cape Town, Sir Charles Metcalfe presiding. The 

 main impetus to the movement for such an organisation was 

 given by Mr.T. Reunert, M.Inst.C.K., a resident of Johannes- 

 burg, and he, indeed, may be regarded as the father and 

 founder of the South African Association. The first meeting 

 was held at Cape Town in 1903, under the Presidency of 

 Sir David Gill, with a membership of 700, since increased to 

 over 2000 ; the second at Johannesburg, Sir C. Metcalfe, 

 presiding. No meeting is to be held in the present year. 



The Royal Observatory 

 ©lI the Ca^pe. 



The first oflicial document relating to the Royal Ob- 

 servatory at the Cape of Good Hope is a minute of 

 proceedings of a meeting of " Commissioners appointed 

 ijy .\ct of Parliament for more effectually discovering 

 the longitude at sea," it is dated February 3, i8:;o. 

 The establishment of an observatory was proposed at 

 this meeting by Mr. Davies Gilbert, M.P., and seconded 

 by Sir Joseph Banks, P. R.S. By an Order in Council 

 nuthority was given on October 20, 1S20, for the estab- 

 lishment of a staff, consisting of an astrononier and 



rttoto hy Maun d Foi.J 



SIR DAVID QILL, K.C.B., F.R.S., 

 H.M. Astronomer at the Cape ol Good Hope. 



assistant astronomer. The equipment was a 25-feet 

 zenith micrometer by Troughton, a transit by Dollond, 

 a 6-foot mural circle by Jones, and an equatorial sector 

 and a 6-fect .Vewtonian reflector were provided from 

 (jreenwich. Although the primary oljjcct in founding 

 the observatory was to provide ships sailing to India 

 and the East with accurate time, it was recognised that 

 a suitable opportunity had presented itself for founding 

 a great national observatory in the Southern Hemi- 

 sphere. The first astionomer was the Rev. Fcaron 

 Fallows, F.R..S., who arrived at the Cape in 1821, 

 bringing with him some portable instruments. His 

 first instructions were to find a suitable site. The pre- 

 sent one, it should be said, was chosen after trying 

 several others, which had to be abandoned on account 

 of drifting sand or of cloud, and many were the annoy- 

 ances and discomforts encountered during these pre- 

 liminary efforts. For over three years I'allows lived 

 in a hut superintending the building f)f the observatory. 

 At last, in 1829, he found it possible to begin regul:ir 

 astronomical work, but he could not accomplish much 



